A typical scroll machine has an orbiting scroll member having a spiral wrap on one face thereof, a non-orbiting scroll member having a spiral wrap on one face thereof, said wraps being intermeshed with one another, and means for causing said orbiting scroll member to orbit about an axis with respect to said non-orbiting scroll member, whereby said wraps will create pockets of progressively changing volume.
To maximize efficiency, it is important for the wrap tips of each scroll member to sealingly engage the end plate of the other scroll member so that there is minimum leakage therebetween. One way this has been accomplished, other than by using tip seals (which are very difficult to assemble and which often present reliability problems) is by using fluid under pressure to axially bias one of the scroll members against the other scroll member. This, of course, requires seals in order to isolate the biasing fluid at the desired pressure. Accordingly, there is a continuing need in the field of scroll machines for improved axial biasing techniques including improved seals to facilitate same.
The seals of the present invention are embodied in a compressor and suited for use in machines which use discharge pressure alone, discharge and an independent intermediate pressure, or solely an intermediate pressure only, in order to provide the necessary axial biasing forces to enhance tip sealing. In addition, the seals of the present invention, which in most embodiments are three seals in one, are suitable particularly for use in applications which bias the non-orbiting scroll.
It is therefore one of the primary objects of the present invention to provide an improved seal which is relatively simple in construction, easy to install and inspect, and which effectively provides the complex sealing functions desired. The seals of the present invention provide significant additional advantages. For example, the seal has been discovered to be particularly sensitive to the pressure ratio of the scroll machine and consequently provides particularly good protection against vacuum conditions such as caused by reverse rotation or a blocked suction condition. In this condition, the seal will become ineffective and thus permit discharge gas to be bypassed directly into a zone of suction gas at suction gas pressure. This prevents the creation of a high vacuum on the inlet side of the compressor which might otherwise occur and which could cause excessive and damaging forces pulling the scroll members together. Even more importantly, it prevents the arcing or burning of the motor protector connector pins which has been observed to occur under some vacuum conditions.
The seals of the present invention also, in some applications, provide a degree of temperature protection, particularly in motor-compressors where suction gas is used to cool the motor. This is because the seal will leak from the high side to the low side at pressure differentials which are significantly higher than those for which the machine was designed. This leakage of discharge fluid to the suction side of the compressor will cause the machine to have a reduced output and the resulting heat build-up within the compressor enclosure due to the reduced flow of cooling gas will cause the standard motor protector to trip and shut the machine down. This characteristic of the seals of the present invention therefore provides a degree of protection in certain applications from excessive discharge temperatures which could result from loss of working fluid charge, or from a blocked condensor fan in a refrigeration system, or from an excessive discharge pressure (for whatever reason). All of these undesirable conditions will cause a scroll machine to function at a pressure ratio greater than that which is designed into the machine in terms of its predetermined fixed volume ratio.
These and other advantages of the present invention will become more apparent when viewed in light of the accompanying drawings and following detailed description.